CN110573944B - Light modulation device - Google Patents

Abstract

The present application relates to a light modulation device and use thereof. The present application can provide a light modulation device having both excellent mechanical characteristics and optical characteristics by using a polymer film that is also optically anisotropic and mechanically anisotropic as a substrate. Further, the present application may provide eyewear comprising a light modulation device comprising a flexible polymeric film substrate and may be applied to a wide variety of designs, such as folded forms.

Description

Light modulation device

Technical Field

The present application relates to light modulation devices.

The present application claims rights based on the priority rights of korean patent application No. 10-2017-0054964 filed on 28.4.2017, korean patent application No. 10-2018-0003783, korean patent application No. 10-2018-0003784, korean patent application No. 10-2018-0003785, korean patent application No. 10-2018-0003786, korean patent application No. 10-2018-0003787, korean patent application No. 10-2018-0003788, korean patent application No. 10-2018-0003789, and korean patent application No. 10-2018-0003789, filed on 12.1.2018.4.2018, the disclosures of which are incorporated herein by reference in their entireties.

Background

Light modulation devices in which a light modulation layer containing a liquid crystal compound or the like is positioned between two substrates facing each other have been used in various applications.

For example, in patent document 1 (european patent application publication No. 0022311), there is known a transmittance variable device using a so-called GH cell in which a mixture of a liquid crystal host material and a dichroic dye guest is applied as a light modulation layer.

In such a device, a glass substrate having excellent optical isotropy and good dimensional stability is mainly used as a substrate.

While the application of the light modulation device is expanded to eyewear or smart windows (e.g., skylights) without being limited to display devices and the shape of the device is not limited to a plane but various designs such as a folded form are applied thereto and it appears that a so-called flexible device or the like is required, an attempt is made to apply a polymer film substrate as a substrate of the light modulation device instead of a glass substrate.

In the case of applying a polymer film substrate, in order to secure characteristics similar to those of a glass substrate, it is known to be advantageous to apply a film substrate which is optically isotropic as much as possible and has a small difference in physical characteristics in the so-called MD direction (machine direction) and TD direction (transverse direction).

Disclosure of Invention

Technical problem

The present application relates to light modulation devices. An object of the present application is to provide a light modulation device excellent in both mechanical characteristics and optical characteristics by applying an optically and mechanically anisotropic polymer film as a substrate.

Technical scheme

In the present specification, terms such as vertical, horizontal, orthogonal, or parallel in terms of defining angles mean substantially vertical, horizontal, orthogonal, or parallel within a range that does not impair the intended effect, and the range of vertical, horizontal, orthogonal, or parallel includes errors such as manufacturing errors or deviations (variations). For example, each of the foregoing may include an error within about ± 15 degrees, an error within about ± 10 degrees, or an error within about ± 5 degrees.

Among the physical properties mentioned herein, when the measured temperature affects the relevant physical property, the physical property is a physical property measured at room temperature unless otherwise specified.

In the present specification, the term room temperature is a temperature in a state without being particularly heated or cooled, which may mean a temperature in a range of about 10 ℃ to 30 ℃, for example, a temperature of about 15 ℃ or more, 18 ℃ or more, 20 ℃ or more, or about 23 ℃ or more and about 27 ℃ or less. Unless otherwise stated, the units for temperatures referred to herein are in degrees celsius.

The phase difference and refractive index mentioned herein mean refractive indices for light having a wavelength of about 550nm, unless otherwise specified.

Unless otherwise specified, the angle formed by any two directions referred to herein may be an acute angle formed by the two directions to an obtuse angle, or may be a small angle of angles measured in clockwise and counterclockwise directions. Thus, unless otherwise indicated, the angles referred to herein are positive. However, if necessary, in order to display the measurement direction between the angles measured in the clockwise direction or the counterclockwise direction, either one of the angle measured in the clockwise direction and the angle measured in the counterclockwise direction may be represented as a positive number, and the other angle may be represented as a negative number.

The liquid crystal compound contained in the active liquid crystal layer or the light modulation layer herein may also be referred to as a liquid crystal molecule, a liquid crystal host (when contained together with a dichroic dye guest), or simply as a liquid crystal.

The present application relates to light modulation devices. The term light modulation device may mean a device capable of switching between at least two or more different light states. Here, the different light states may mean states in which at least transmittance and/or reflectance is different.

Examples of states that the light modulation device may achieve include a transmissive mode state, a blocking mode state, a high reflective mode state, and/or a low reflective mode state.

In one example, the light modulation device may be at least a device capable of switching between a transmissive mode state and a blocking mode state, or may be a device capable of switching between a highly reflective mode and a low reflective mode.

The light modulating device may have a transmittance in the transmissive mode of at least 20% or greater, 25% or greater, 30% or greater, 35% or greater, 40% or greater, 45% or greater, 50% or greater, 55% or greater, 60% or greater, 65% or greater, 70% or greater, 75% or greater, or around 80% or greater. Further, the transmittance of the light modulating device in the blocking mode may be 60% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, or 5% or less. Since the higher the transmittance in the transmissive mode state is more advantageous and the lower the transmittance in the blocking mode state is more advantageous, the upper limit of the transmittance in the transmissive mode state and the lower limit of the transmittance in the blocking mode state are not particularly limited, wherein in one example, the upper limit of the transmittance in the transmissive mode state may be about 100% and the lower limit of the transmittance in the blocking mode state may be about 0%.

In one example, in a light modulation device that is capable of switching between a transmission mode state and a blocking mode state, a difference between a transmittance in the transmission mode state and a transmittance in the blocking mode state (transmission mode-blocking mode) may be 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, or 40% or more, or may be 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, or 45% or less.

The transmittance may be, for example, a linear light transmittance. Linear light transmission is the percentage of the ratio of light transmitted in the same direction as the incident direction to light incident on the device. For example, if the device is in the form of a film or sheet, the percentage of light transmitted through the device in a direction parallel to the normal direction of the surface of the film or sheet, among light incident in a direction parallel to the normal direction, may be defined as the transmittance.

The reflectance of the light modulation device in the high reflection mode state may be at least 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, or 40% or more. Further, the reflectance of the light modulation device in the low reflection mode state may be 20% or less, 15% or less, 10% or less, 7% or less, 6% or less, 5% or less, or 4% or less. Since the higher reflectance in the high reflectance mode is more advantageous and the lower reflectance in the low reflectance mode is more advantageous, the upper limit of the reflectance in the high reflectance mode state and the lower limit of the reflectance in the low reflectance mode state are not particularly limited, wherein in one example, the reflectance in the high reflectance mode state may be about 100% or less, about 90% or less, about 80% or less, about 70% or less, about 60% or less, 55% or less, 50% or less, or about 40% or less, and the reflectance in the low reflectance mode state may be about 0% or more, about 0.1% or more, 1% or more, 3% or more, or 5% or more.

Further, in an example, in a light modulation device capable of switching between a low reflection mode state and a high reflection mode state, a difference between a reflectance in the high reflection mode state and a reflectance in the low reflection mode state (high reflection mode-low reflection mode) may be 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, or 40% or more, or may be 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, or 45% or less.

The above-mentioned transmittance and reflectance may each be a transmittance or reflectance for any wavelength in the visible light region, for example, for any wavelength in the range of about 400nm to 700nm or about 380nm to 780nm, or a transmittance or reflectance for the entire visible light region, a maximum or minimum transmittance or reflectance in the transmittance or reflectance for the entire visible light region, or an average value of the transmittance or reflectance in the visible light region.

The light modulation device of the present application may be designed to switch between at least two or more states selected from any one state of a transmission mode, a blocking mode, a high reflection mode, and a low reflection mode, and another state. If necessary, other states than the above states, for example, other third states or more states including an intermediate transmittance state in the transmissive mode state and the blocking mode state, an intermediate reflectance state in the high reflection mode state and the low reflection mode state, and the like may also be realized.

The switching of the light modulation device may be controlled depending on whether an external signal, such as a voltage signal, is applied. For example, the light modulation device may maintain any one of the above states in a state where an external signal such as a voltage is not applied, and then may be switched to another state when a voltage is applied. By varying the intensity, frequency and/or shape of the applied voltage, the state of the mode may be changed or a third, different mode state may also be achieved.

The light modulation device of the present application may basically include a light modulation film layer having two substrates disposed opposite to each other and a light modulation layer positioned between the substrates. Hereinafter, for convenience, any one of two substrates disposed opposite to each other is referred to as a first substrate, and the other substrate is referred to as a second substrate.

Fig. 1 is a cross-sectional view of an exemplary light modulating film layer (active liquid crystal film layer) of the present application, wherein the light modulating film layer may include a first polymer film substrate 11 and a second polymer film substrate 13 and a light modulating layer 12 present between the first polymer film substrate and the second polymer film substrate.

In the light modulation device of the present application, a polymer film substrate is applied as a substrate. The substrate of the light modulating device may not include a glass layer. By providing a polymer film substrate having high anisotropy optically and anisotropy even in mechanical properties in a specific relationship, the present application can constitute a device having no optical defect such as a so-called iridescence phenomenon but having excellent mechanical properties. Such results are contrary to the general knowledge of the prior art: an optically isotropic substrate must be applied to ensure excellent optical characteristics and a substrate having isotropic mechanical characteristics is advantageous in terms of mechanical characteristics such as dimensional stability of a device.

In the present specification, a polymer film substrate having anisotropy in optical and mechanical properties may be referred to as an asymmetric substrate or an asymmetric polymer film substrate. Here, the fact that the polymer film substrate is optically anisotropic is the case with the above-described in-plane retardation, and the fact that it is anisotropic in mechanical properties is the case with the physical properties described below.

Hereinafter, the physical property of the polymer film substrate referred to herein may be a physical property of the polymer film substrate itself, or a physical property in a state where an electrode layer is formed on one side of the polymer film substrate. In this case, the electrode layer may be an electrode layer formed in a state where the polymer film substrate is included in the optical device.

The measurement of the physical properties of each of the polymeric film substrates mentioned herein was performed according to the method described in the examples section of the present specification.

In one example, the in-plane retardation of the first polymeric film substrate and the second polymeric film substrate may be about 4,000nm or greater, respectively.

In this specification, in-plane retardation (Rin) may mean a value calculated by the following equation 1.

[ equation 1]

Rin＝dX(nx-ny)

In equation 1, Rin is an in-plane retardation, d is a thickness of the polymer film substrate, nx is a refractive index in a slow axis direction in a plane of the polymer film substrate, and ny is a refractive index in a fast axis direction, which is a refractive index in an in-plane direction perpendicular to the slow axis direction.

The in-plane retardation of each of the first polymer film substrate and the second polymer film substrate may be 4,000nm or more, 5,000nm or more, 6,000nm or more, 7,000nm or more, 8,000nm or more, 9,000nm or more, 10,000nm or more, 11,000nm or more, 12,000nm or more, 13,000nm or more, 14,000nm or more, or around 15,000nm or more. The in-plane retardation of each of the first polymeric film substrate and the second polymeric film substrate can be about 50,000nm or less, about 40,000nm or less, about 30,000nm or less, 20,000nm or less, 18,000nm or less, 16,000nm or less, 15,000nm or less, or about 12,000nm or less.

As a polymer film having such a large retardation, a film called a so-called high stretch PET (poly (ethylene terephthalate)) film, SRF (super retardation film), or the like is generally known. Thus, in the present application, the polymeric film substrate may be, for example, a polyester film substrate.

Films having extremely high retardation as above are known in the art, and such films exhibit high asymmetry even in mechanical properties by high-power stretching or the like during the production process and optically high anisotropy. Representative examples of polymer film substrates in the state of the art are polyester films such as PET (poly (ethylene terephthalate)) films, and for example, there are films of the SRF (ultra-retardation film) series available under the trade name Toyobo co.

Unless otherwise specified, the thickness direction retardation value of each of the polymer film substrates as calculated by equation 2 below may be about 1,000nm or less.

[ equation 2]

Rth＝dX(nx-ny)

In equation 2, Rth is the thickness direction retardation, d is the thickness of the polymer film substrate, and ny and nz are the refractive indices in the y-axis and z-axis directions of the polymer film substrate, respectively. The y-axis of the polymer film substrate is the in-plane fast axis direction, and the z-axis direction means the thickness direction of the polymer film substrate.

The polymeric film substrate may also have a gas permeability of less than 0.002GPU at room temperature. The gas permeability of the polymeric film substrate can be, for example, 0.001GPU or less, 0.0008GPU or less, 0.006GPU or less, 0.004GPU or less, 0.002GPU or less, or 0.001GPU or less. When the gas permeability of the polymer film substrate is within the above range, a light modulation device having excellent durability in which generation of voids due to external gas is suppressed can be provided. The lower limit of the range of the gas permeability is not particularly limited. That is, the smaller the value, the more favorable the gas permeability.

In one example, in each polymer film substrate, a ratio (E1/E2) of an elongation (E1) in any one first direction in a plane to an elongation (E2) in a second direction perpendicular to the first direction may be 3 or more. In another example, the ratio (E1/E2) can be about 3.5 or greater, 4 or greater, 4.5 or greater, 5 or greater, 5.5 or greater, 6 or greater, or 6.5 or greater. In another example, the ratio (E1/E2) can be about 20 or less, 18 or less, 16 or less, 14 or less, 12 or less, 10 or less, 8 or less, or 7.5 or less.

As used herein, the terms "first direction", "second direction", and "third direction" of a polymeric film substrate are each any in-plane direction of the film substrate. For example, when the polymer film substrate is a stretched polymer film substrate, the in-plane direction may be an in-plane direction formed by the MD direction (machine direction) and the TD direction (transverse direction) of the polymer film substrate. In one example, the first direction described herein may be any one of a slow axis direction and a fast axis direction of the polymer film substrate, and the second direction may be the other one of the slow axis direction and the fast axis direction. In another example, when the polymer film substrate is a stretched polymer film substrate, the first direction may be any one of an MD direction (machine direction) and a TD direction (transverse direction), and the second direction may be the other one of the MD direction (machine direction) and the TD direction (transverse direction).

In one example, the first direction of the polymeric film substrate referred to herein may be the TD direction or the slow axis direction.

Here, the elongation of each of the first and second polymer film substrates in the first direction (e.g., the slow axis direction or TD direction described above) may be 15% or more, or 20% or more. In another example, the elongation may be about 25% or greater, 30% or greater, 35% or greater, or 40% or greater, or may be about 100% or less, 90% or less, 80% or less, 70% or less, about 60% or less, 55% or less, 50% or less, or 45% or less.

In one example, in each of the first and second polymeric film substrates, an elongation in a third direction (E3) forming an angle in a range of 40 degrees to 50 degrees or about 45 degrees with the first and second directions, respectively, is greater than an elongation in the first direction (e.g., the slow axis direction or TD direction described above) (E1), wherein a ratio of the elongation in the third direction (E3) to the elongation in the second direction (E2) (E3/E2) may be 5 or greater.

In another example, the ratio (E3/E2) may be 5.5 or greater, 6 or greater, 6.5 or greater, 7 or greater, 7.5 or greater, 8 or greater, or 8.5 or greater, and may be about 20 or less, 18 or less, 16 or less, 14 or less, 12 or less, or 10 or less.

Here, the elongation of each of the first and second polymer film substrates in the third direction may be 30% or more. In another example, the elongation may be about 35% or greater, 40% or greater, 45% or greater, 50% or greater, or 55% or greater, or may be about 80% or less, 75% or less, 70% or less, or 65% or less.

In each of the first and second polymeric film substrates, a ratio (CTE2/CTE1) of a coefficient of thermal expansion in the second direction (CTE2) to a coefficient of thermal expansion in the first direction (CTE1), for example, the slow axis direction or TD direction described above, may be 1.5 or greater. The coefficients of thermal expansion (CTE1, CTE2) are each values determined in the temperature range of 40 ℃ to 80 ℃. In another example, the ratio (CTE2/CTE1) may be about 2 or greater, about 2.5 or greater, 3 or greater, or 3.5 or greater, or may be 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, or 4 or less.

The coefficient of thermal expansion in the second direction (CTE2) may be in a range of 5 ppm/deg.C to 150 ppm/deg.C. The coefficient of thermal expansion can be about 10 ppm/deg.C or greater, 15 ppm/deg.C or greater, 20 ppm/deg.C or greater, 25 ppm/deg.C or greater, 30 ppm/deg.C or greater, 35 ppm/deg.C or greater, 40 ppm/deg.C or greater, 45 ppm/deg.C or greater, 50 ppm/deg.C or greater, 55 ppm/deg.C or greater, 60 ppm/deg.C or greater, 65 ppm/deg.C or greater, 70 ppm/deg.C or greater, 75 ppm/deg.C or greater, or 80 ppm/deg.C or greater, or can be 140 ppm/deg.C or less, 130 ppm/deg.C or less, 120 ppm/deg.C or less, 100 ppm/deg.C or less, 95 ppm/deg.C or less, 90 ppm/deg.C or less, 85 ppm/deg.C or less, 80 ppm/deg.C or less, 40 ppm/deg.C or less, 30 ppm/deg.C or less, or less, Or 25 ppm/deg.C or less.

In each of the first polymer film substrate and the second polymer film substrate, a ratio (YM1/YM2) of an elastic modulus (YM1) in the first direction (e.g., the above-described slow axis direction or TD direction) to an elastic modulus (YM2) in the second direction may be 1.5 or more. In another example, the ratio (YM1/YM2) may be about 2 or greater, or may be 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2.5 or less.

The modulus of elasticity (YM1) in the first direction (e.g., the slow axis direction or TD direction described above) may be in the range of about 2GPa to 10 GPa. In another example, the modulus of elasticity (YM1) may be about 2.5GPa or greater, 3GPa or greater, 3.5GPa or greater, 4GPa or greater, 4.5GPa or greater, 5GPa or greater, or 5.5GPa or greater, or may also be about 9.5GPa or less, 9GPa or less, 8.5GPa or less, 8GPa or less, 7.5GPa or less, 7GPa or less, 6.5GPa or less, or 6GPa or less.

The elastic modulus is a so-called young's modulus, which is measured according to the method of the examples described below.

In each of the first and second polymeric film substrates, a ratio (MS1/MS2) of a maximum stress (MS1) in the first direction (e.g., the above-described slow axis direction or TD direction) to a maximum stress (MS2) in the second direction may be 1.5 or more. In another example, the ratio (MS1/MS2) may be about 2 or greater, or may be 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2.5 or less.

The maximum stress (MS1) in the first direction (e.g., the slow axis direction or TD direction described above) may be in the range of about 80MPa to 300 MPa. In another example, the maximum stress (MS1) can be about 90MPa or greater, about 100MPa or greater, about 110MPa or greater, about 120MPa or greater, about 130MPa or greater, about 140MPa or greater, about 150MPa or greater, about 155MPa or greater, 160MPa or greater, 165MPa or greater, 170MPa or greater, 175MPa or greater, or 180MPa or greater, or can also be about 300MPa or less, about 290MPa or less, about 280MPa or less, about 270MPa or less, about 260MPa or less, about 250MPa or less, about 245MPa or less, 240MPa or less, 235MPa or less, 230MPa or less, 225MPa or less, 220MPa or less, 215MPa or less, 210MPa or less, 205MPa or less, 200MPa or less, 195MPa or less, 190MPa or less.

In the light modulation device of the present application, an absolute value of an angle formed by the first direction of the first polymer film substrate and the first direction of the second polymer film substrate may be in a range of 0 degree to 10 degrees or 0 degree to 5 degrees, or the first directions may be substantially horizontal to each other. The first direction may be the slow axis direction or the TD direction of the polymer film substrate as described above.

Since the device is configured by disposing the polymer film substrate having asymmetric optical characteristics and mechanical characteristics to have such a specific relationship as described above, the present application can realize excellent optical characteristics and mechanical characteristics.

Although the reason for achieving such an effect is not clear, it is considered to be because a better balance of optical characteristics and mechanical characteristics is ensured by similarly controlling the high asymmetry possessed by at least two polymer film substrates and setting the two asymmetries to be symmetrical again based on a specific axis, as compared with the application of a film having an isotropic structure.

The thickness of each of the first polymer film substrate and the second polymer film substrate is not particularly limited and may be set within an appropriate range according to the purpose. Typically, the thickness may be in the range of about 10 μm to 200 μm.

As described above, a representative example of a polymer film having high optical and mechanical asymmetry as above is a stretched PET (polyethylene terephthalate) film or the like called a so-called high-power stretched polyester film, and such a film is industrially easily available.

In general, the stretched PET film is a uniaxially stretched film of one or more layers produced by forming a PET-based resin into a film by melting/extrusion and stretching the film, or a biaxially stretched film of one or more layers produced by stretching the film in the longitudinal and transverse directions after film formation.

The PET-based resin generally means a resin in which 80 mol% or more of the repeating units are ethylene terephthalate, which may further contain other dicarboxylic acid components and diol components. The other dicarboxylic acid component is not particularly limited, but may include, for example, isophthalic acid, p- β -oxyethoxybenzoic acid, 4 '-dicarboxybiphenyl, 4' -dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, and/or 1, 4-dicarboxycyclohexane, and the like.

The other diol component is not particularly limited, but may include propylene glycol, butylene glycol, neopentyl glycol, diethylene glycol, cyclohexanediol, an ethylene oxide adduct of bisphenol a, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and/or the like.

If necessary, the dicarboxylic acid component or the diol component may be used in combination of two or more. Furthermore, oxycarboxylic acids, such as p-oxybenzoic acid, may also be used in combination. Further, as other copolymerization components, a diol component or a dicarboxylic acid component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, and the like may also be used.

As a method for producing a PET-based resin, the following method is employed: a method of directly polycondensing terephthalic acid, ethylene glycol and/or (if necessary) another dicarboxylic acid or another diol, a method of polycondensing a dialkyl ester of terephthalic acid and ethylene glycol and/or (if necessary) a dialkyl ester of another dicarboxylic acid or another diol by transesterification, and a method of polycondensing an ethylene glycol and/or (if necessary) another diol of terephthalic acid and/or (if necessary) another dicarboxylic acid, and the like.

For each polymerization reaction, a polymerization catalyst containing an antimony-based compound, a titanium-based compound, a germanium-based compound, or an aluminum-based compound, or a polymerization catalyst containing a composite compound may be used.

The polymerization reaction conditions may be appropriately selected according to the monomers, the catalyst, the reaction equipment, and the intended physical properties of the resin, and are not particularly limited, but for example, the reaction temperature is generally about 150 ℃ to about 300 ℃, about 200 ℃ to about 300 ℃, or about 260 ℃ to about 300 ℃. Further, the reaction pressure is usually from atmospheric pressure to about 2.7Pa, wherein the pressure may be reduced in the latter half of the reaction.

The polymerization reaction is carried out by volatilizing the remaining reactants such as glycol, alkyl compound or water.

The polymerization apparatus may be a polymerization apparatus which is completed by one reaction tank or a plurality of reaction tanks are connected. In this case, the polymerization is carried out while the reactants are transferred between the reaction tanks, depending on the degree of polymerization. Further, a method of: wherein a horizontal reaction apparatus is provided in the latter half of the polymerization and the reactants are volatilized while being heated/kneaded.

After completion of the polymerization, the resin is discharged from the reaction tank or the horizontal reaction apparatus in a molten state, and then obtained in the form of a sheet cooled and pulverized in a cooling drum or a cooling belt, or in the form of pellets which are cut after being introduced into an extruder and extruded in a strand form. Further, solid-phase polymerization may be carried out as needed to increase the molecular weight or reduce the low-molecular weight component. As the low molecular weight component that can be contained in the PET resin, a cyclic trimer component can be exemplified, but the content of such a cyclic trimer component in the resin is usually controlled to 5,000ppm or less, or 3,000ppm or less.

When the PET-based resin is dissolved in a mixed solvent of phenol/tetrachloroethane (50/50 (weight ratio)) and expressed as an intrinsic viscosity measured at 30 ℃, the molecular weight of the PET-based resin is generally in the range of 0.45dL/g to 1.0dL/g, 0.50dL/g to 1.0dL/g, or 0.52dL/g to 0.80 dL/g.

Further, the PET-based resin may contain additives as necessary. The additives may include lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light stabilizers, impact resistance improvers, and the like. The amount added thereof is preferably within a range that does not adversely affect the optical characteristics.

For the formulation of such additives and the film formation to be described below, the PET-based resin is used in the form of pellets assembled by a common extruder. The size and shape of the pellets are not particularly limited, but they are generally cylindrical, spherical or oblate spheroid in shape, both in height and diameter of 5mm or less. The PET-based resin thus obtained may be molded into a film form and subjected to a stretching process to obtain a transparent and homogeneous PET film having high mechanical strength. The production method is not particularly limited, and for example, the following method is employed.

Pellets made of the dried PET resin are supplied to a melt extrusion apparatus, heated to a melting point or higher and melted. Next, the molten resin is extruded from the die and quenched and solidified on a rotating cooling drum to a temperature below the glass transition temperature to obtain an unstretched film in a substantially amorphous state. The melting temperature is determined according to the melting point of the PET-based resin to be used or an extruder, which is not particularly limited, but is generally 250 to 350 ℃. In order to improve the planarity of the film, it is also preferable to enhance the adhesion between the film and the rotating cooling drum, and it is preferable to employ an adhesion method by electrostatic application or an adhesion method by liquid coating. The bonding method by electrostatic application is generally a method of: wherein a linear electrode is disposed on the upper surface side of the film in a direction perpendicular to the flow of the film and a direct current voltage of about 5kV to 10kV is applied to the electrode to supply an electrostatic charge to the film, thereby improving adhesion between the rotary cooling drum and the film. Further, the bonding method by liquid coating is a method of improving bonding between a rotary cooling drum and a film by uniformly applying a liquid to all or part of the surface of the rotary cooling drum (for example, only a portion in contact with both film ends). If necessary, they may be used in combination. The PET-based resin to be used may be mixed with two or more resins, or resins having different structures or compositions, if necessary. For example, it may include using a mixture of pellets and unblended pellets blended with a particulate filler material as an anti-blocking agent, an ultraviolet absorber, an antistatic agent or the like, and the like.

Further, the lamination number of the film to be extruded may also be two or more layers, if necessary. For example, it may include preparing pellets in which a particulate filler material as an anti-blocking agent is blended and unblended pellets, and supplying from another extruder to the same die to extrude a film composed of two three layers (i.e., "filler material blended/unblended/filler material blended"), and the like.

The unstretched film is usually first longitudinally stretched in the extrusion direction at a temperature not lower than the glass transition temperature. The stretching temperature is usually 70 ℃ to 150 ℃, 80 ℃ to 130 ℃, or 90 ℃ to 120 ℃. Further, the stretching ratio is usually 1.1 to 6 times or 2 to 5.5 times. The stretching may be ended once or may be divided more than once as desired.

Thereafter, the thus obtained longitudinally stretched film may be subjected to a heat treatment. Then, if necessary, relaxation treatment may be performed. The heat treatment temperature is usually 150 ℃ to 250 ℃, 180 ℃ to 245 ℃, or 200 ℃ to 230 ℃. Further, the heat treatment time is usually 1 second to 600 seconds, or 1 second to 300 seconds, or 1 second to 60 seconds.

The temperature of the relaxation treatment is usually 90 ℃ to 200 ℃ or 120 ℃ to 180 ℃. Further, the amount of relaxation is typically 0.1% to 20%, or 2% to 5%. The relaxation treatment temperature and the relaxation amount may be set so that the thermal shrinkage rate of the PET film after the relaxation treatment at 150 ℃ is 2% or less.

In the case of obtaining a uniaxially stretched film and a biaxially stretched film, the transverse stretching is usually performed by a tenter after the longitudinal stretching treatment or (if necessary) after the heat treatment or the relaxation treatment. The stretching temperature is usually 70 ℃ to 150 ℃, 80 ℃ to 130 ℃ or 90 ℃ to 120 ℃. Further, the stretching ratio is usually 1.1 to 6 times or 2 to 5.5 times. Thereafter, heat treatment and, if necessary, relaxation treatment may be performed. The heat treatment temperature is usually 150 ℃ to 250 ℃, or 180 ℃ to 245 ℃, or 200 ℃ to 230 ℃. The heat treatment time is generally 1 second to 600 seconds, 1 second to 300 seconds, or 1 second to 60 seconds.

The temperature of the relaxation treatment is usually 100 ℃ to 230 ℃, 110 ℃ to 210 ℃, or 120 ℃ to 180 ℃. Further, the amount of relaxation is typically 0.1% to 20%, 1% to 10%, or 2% to 5%. The relaxation treatment temperature and the relaxation amount may be set so that the thermal shrinkage rate of the PET film after the relaxation treatment at 150 ℃ is 2% or less.

In the uniaxial stretching treatment and the biaxial stretching treatment, in order to reduce deformation of the orientation main axis by bending, the heat treatment may be performed again or the stretching treatment may be performed after the transverse stretching. The maximum value of the deformation of the orientation main axis by bending with respect to the stretching direction is generally within 45 degrees, within 30 degrees, or within 15 degrees. Here, the stretching direction also means a stretching major direction in the longitudinal stretching or the transverse stretching.

In biaxial stretching of a PET film, the transverse direction stretching ratio is generally slightly greater than the longitudinal direction stretching ratio, wherein the stretching direction refers to a direction perpendicular to the long direction of the film. Further, uniaxial stretching is generally stretching in the transverse direction as described above, wherein the stretching direction also refers to the direction perpendicular to the longitudinal direction.

Further, the orientation principal axis means a molecular orientation direction at any point on the stretched PET film. Further, the deformation of the orientation main axis with respect to the stretching direction refers to an angle difference between the orientation main axis and the stretching direction. Further, the maximum value thereof means the maximum value among values in the perpendicular direction with respect to the long direction.

The direction of the principal axis of orientation is known, and may be measured using, for example, a retardation film/optical material inspection apparatus RETS (manufactured by Otsuka Densi KK) or a molecular orientation system MOA (manufactured by Oji Scientific Instruments).

The stretched PET film used in the present application may be imparted with an antiglare property (haze). The method of imparting the antiglare property is not particularly limited, and for example, the following methods are employed: a method of mixing inorganic fine particles or organic fine particles into a raw material resin to form a film; a method of forming a stretched film from an unstretched film having a layer in which inorganic fine particles or organic fine particles are mixed on one side based on a method of manufacturing a film; or a method of forming an antiglare layer by coating a coating liquid formed by mixing inorganic fine particles or organic fine particles with a curable binder resin on one side of a stretched PET film and curing the binder resin; and so on.

The inorganic fine particles for imparting the antiglare property are not particularly limited, but may include, for example, silica, colloidal silica, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate and the like. In addition, the organic fine particles are not particularly limited, but may include, for example, crosslinked polyacrylic acid particles, methyl methacrylate/styrene copolymer resin particles, crosslinked polystyrene particles, crosslinked polymethyl methacrylate particles, silicone resin particles, polyimide particles, and the like. The haze value of the thus obtained stretched PET film imparted with the antiglare property may be in the range of 6% to 45%.

Functional layers such as a conductive layer, a hard coat layer, and a low reflection layer may also be laminated on the stretched PET film imparted with the antiglare property. Further, as the resin composition constituting the antiglare layer, a resin composition having any of these functions may be selected.

The haze value can be measured according to JIS K7136 using, for example, a haze permeameter HM-150 (manufactured by Murakami Color Research Laboratory, Co., Ltd.). In measuring the haze value, in order to prevent the film from warping, for example, a measurement sample in which the film surface is bonded to a glass substrate using an optically transparent pressure-sensitive adhesive so that the surface imparted with the antiglare property becomes a surface may be used.

A functional layer other than an antiglare layer or the like may be laminated on one side or both sides of the stretched PET film used in the present application unless the functional layer interferes with the effect of the present application. The functional layers to be laminated may include, for example, a conductive layer, a hard coat layer, a smoothing layer, an easy-slip layer, an anti-blocking layer, an easy-adhesion layer, and the like.

The above-described method for manufacturing a PET film is one exemplary method for obtaining the polymer film substrate of the present application, wherein any kind of commercially available products may be used as long as the polymer film substrate applicable to the present application has the above-described physical properties.

In one example, the polymer film substrate may be a film substrate having an electrode layer formed on one side. Such a film substrate may be referred to as an electrode film substrate. The above-described retardation characteristics, mechanical characteristics, or the like may be used for a polymer film substrate on which an electrode layer is not formed, or for an electrode film substrate.

In the case of an electrode film substrate, each electrode layer may be formed on at least one side of a polymer film substrate, and the first polymer film substrate and the second polymer film substrate may be disposed such that the electrode layers face each other.

As the electrode layer, a known transparent electrode layer may be applied, and for example, a so-called conductive polymer layer, a conductive metal layer, a conductive nanowire layer, or a metal oxide layer (e.g., ITO (indium tin oxide)) may be used as the electrode layer. In addition, various materials and formation methods capable of forming a transparent electrode layer are known, and these materials and methods can be applied without limitation.

Further, an alignment film may be formed on one side of the polymer film substrate, for example, an upper portion of the electrode layer in the case of the electrode film substrate. A known liquid crystal alignment film may be formed as an alignment film, and the kind of alignment film that can be applied according to a desired mode is known.

As described above, in the present application, the light modulation layer included in the light modulation film layer is a functional layer capable of changing transmittance, reflectance, and/or haze of light according to whether an external signal is applied. Such a light modulation layer in which a light state changes depending on whether an external signal or the like is applied may be referred to herein as an active light modulation layer. In one example, when the light modulation layer is a layer containing a liquid crystal compound, the light modulation layer may be referred to as an active liquid crystal layer, where the active liquid crystal layer means a liquid crystal layer in a form in which the liquid crystal compound can be changed in the active liquid crystal layer by applying an external signal. Also, the light modulation film layer including the active liquid crystal layer may be referred to as an active liquid crystal film layer.

An external signal herein may mean any external factor, such as an external voltage, that may affect the behavior of a material (e.g., a light modulating material) included in a light modulating layer. Therefore, the state of no external signal may mean a state in which no external voltage or the like is applied.

In the present application, the type of the light modulation layer is not particularly limited as long as it has the above function, and a known light modulation layer may be applied. In one example, the light modulation layer may be a liquid crystal layer, and a structure including the liquid crystal layer between a first polymer film substrate and a second polymer film substrate disposed opposite to each other may also be referred to herein as a liquid crystal cell or an active liquid crystal film layer.

Exemplary light modulation devices may have excellent durability against gas permeability. In one example, the light modulation device can have a void generation rate of 20% or less when stored at a temperature of 60 ℃ and a relative humidity of 85%. Void generation rate may mean the percentage of the number of void generating samples relative to the number of samples used in the void generation assessment. In another example, the first polymer film substrate and the second polymer film substrate may be substrates heat-treated at a temperature of 130 ℃ for 1 hour, wherein a light modulation device including such a polymer film substrate may not cause voids due to inflow of external gas within 500 hours when stored at a temperature of 60 ℃ and a relative humidity of 85%. As described above, this may be achieved by arranging the transverse directions of the first and second polymeric film substrates to be parallel to each other.

In one example, the light modulation layer may be an active liquid crystal layer including liquid crystal molecules (liquid crystal host) and dichroic dye. Such a liquid crystal layer may be referred to as a guest-host liquid crystal layer (GHLC layer). In this case, a structure including a light modulation layer between polymer film substrates may be referred to as an active liquid crystal film layer. In the present specification, the term "GHLC layer" may mean a layer: the dichroic dyes may be arranged together according to the arrangement of liquid crystal molecules to exhibit anisotropic light absorption characteristics with respect to an alignment direction of the dichroic dyes and a direction perpendicular to the alignment direction, respectively. For example, a dichroic dye is a substance in which the absorptivity of light varies with the polarization direction, wherein if the absorptivity of light polarized in the long axis direction is large, it may be referred to as a p-type dye, and if the absorptivity of light polarized in the short axis direction is large, it may be referred to as an n-type dye. In one example, when a p-type dye is used, polarized light vibrating in a long axis direction of the dye may be absorbed, and polarized light vibrating in a short axis direction of the dye may be less absorbed and transmitted. Hereinafter, the dichroic dye is considered to be a p-type dye unless otherwise specified, but the type of dichroic dye applied in the present application is not limited thereto.

In one example, the GHLC layer may be used as an active polarizer. In the present specification, the term "active polarizer" may mean a functional element capable of controlling anisotropic light absorption according to application of an external action. For example, the active GHLG layer can control anisotropic light absorption of polarized light in a direction parallel to the alignment direction of the dichroic dye and polarized light in a perpendicular direction by controlling the alignment of the liquid crystal molecules and the dichroic dye. Since the alignment of the liquid crystal molecules and the dichroic dye may be controlled by applying an external action such as a magnetic field or an electric field, the active GHLC layer may control the anisotropic light absorption according to the application of the external action.

The kind and physical properties of the liquid crystal molecules may be appropriately selected in consideration of the purpose of the present application.

In one example, the liquid crystal molecules may be nematic liquid crystals or smectic liquid crystals. The nematic liquid crystal may mean a liquid crystal in which rod-shaped liquid crystal molecules have no regularity with respect to position but are aligned parallel to a long axis direction of the liquid crystal molecules, and the smectic liquid crystal may mean a liquid crystal in which rod-shaped liquid crystal molecules are regularly aligned to form a layered structure and are regularly aligned in parallel in the long axis direction. According to one example of the present application, nematic liquid crystals may be used as the liquid crystal molecules.

In one example, the liquid crystal molecules may be non-reactive liquid crystal molecules. The non-reactive liquid crystal molecules may mean liquid crystal molecules having no polymerizable group. Here, the polymerizable group may be exemplified by acryl, acryloxy, methacryloxy, carboxyl, hydroxyl, vinyl, epoxy, or the like, but is not limited thereto, and may include a known functional group called a polymerizable group.

The refractive index anisotropy of the liquid crystal molecules may be appropriately selected in consideration of target physical properties such as variable transmittance properties. In the present specification, the term "refractive index anisotropy" may mean a difference between an extraordinary refractive index and an ordinary refractive index of liquid crystal molecules. The refractive index anisotropy of the liquid crystal molecules may be, for example, 0.01 to 0.3. The refractive index anisotropy may be 0.01 or more, 0.05 or more, 0.07 or more, 0.09 or more, or 0.1 or more, and may be 0.3 or less, 0.2 or less, 0.15 or less, 0.14 or less, or 0.13 or less.

When the refractive index anisotropy of the liquid crystal molecules is within the above range, a light modulation device having excellent variable transmittance or reflectance characteristics can be provided. In one example, the lower the refractive index of the liquid crystal molecules is in the above range, the more excellent the light modulation device having the variable transmittance or reflectance characteristics can be provided.

The dielectric constant anisotropy of the liquid crystal molecules may have a positive dielectric constant anisotropy or a negative dielectric constant anisotropy in consideration of a driving method of the target liquid crystal cell. In the present specification, the term "dielectric constant anisotropy" may mean a difference between an extraordinary permittivity (e) and an ordinary permittivity (eo) of liquid crystal molecules. The dielectric anisotropy of the liquid crystal molecules may be, for example, within ± 40, within ± 30, within ± 10, within ± 7, within ± 5, or within ± 3. When the dielectric constant anisotropy of the liquid crystal molecules is controlled within the above range, it may be advantageous in terms of the driving efficiency of the light modulation element.

The liquid crystal layer may include a dichroic dye. Dyes may be included as guest materials. Dichroic dyes can be used, for example, to control the transmittance of a light modulation device according to the orientation of the host material. In the present specification, the term "dye" may mean a material capable of strongly absorbing and/or modifying light in at least a part or all of the range of the visible light region (for example, in a wavelength range of 400nm to 700 nm), and the term "dichroic dye" may mean a material capable of anisotropically absorbing light in at least a part or all of the range of the visible light region.

As the dichroic dye, for example, a known dye known to have a characteristic that can be aligned according to the alignment state of liquid crystal molecules by a so-called host guest effect can be selected and used. Examples of such dichroic dyes include so-called azo dyes, anthraquinone dyes, methine dyes, azomethine dyes, merocyanine dyes, naphthoquinone dyes, tetrazine dyes, phenylene dyes, quarterylene dyes, benzothiadiazole dyes, diketopyrrolopyrrole dyes, squalene dyes, or pyromethylene dyes, etc., but the dyes usable in the present application are not limited thereto. As the dichroic dye, for example, a black dye may be used. Such dyes are known, for example, azo dyes or anthraquinone dyes, etc., but are not limited thereto.

As the dichroic dye, a dye having a dichroic ratio (i.e., a value obtained by dividing absorption of polarized light parallel to the long axis direction of the dichroic dye by absorption of polarized light parallel to the direction perpendicular to the long axis direction) of 5 or more, 6 or more, or 7 or more may be used. The dye may satisfy a dichroic ratio at least a part of wavelengths or any wavelength within a wavelength range of a visible light region (for example, within a wavelength range of about 380nm to 700nm or about 400nm to 700 nm). The upper limit of the dichroic ratio may be, for example, 20 or less, 18 or less, 16 or less, or around 14 or less.

The content of the dichroic dye in the liquid crystal layer may be appropriately selected in consideration of the purpose of the present application. For example, the content of the dichroic dye in the liquid crystal layer may be 0.1 wt% or more, 0.25 wt% or more, 0.5 wt% or more, 0.75 wt% or more, 1 wt% or more, 1.25 wt% or more, or 1.5 wt% or more. The upper limit of the content of the dichroic dye in the liquid crystal layer may be, for example, 5.0 wt% or less, 4.0 wt% or less, 3.0 wt% or less, 2.75 wt% or less, 2.5 wt% or less, 2.25 wt% or less, 2.0 wt% or less, 1.75 wt% or less, or 1.5 wt% or less. When the content of the dichroic dye in the liquid crystal layer satisfies the above range, a light modulation device having excellent variable transmittance characteristics can be provided. In one example, the higher the content of the dichroic dye is in the above range, the more excellent the variable transmittance characteristic of the light modulation device can be provided.

In the liquid crystal layer, the total weight of the liquid crystal molecules and the dichroic dye may be, for example, about 60 wt% or more, 65 wt% or more, 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% or more, and in another example, it may be less than about 100 wt%, 98 wt% or less, or 96 wt% or less.

The liquid crystal layer may switch an alignment state according to whether a voltage is applied. The voltage may be applied to a direction perpendicular or horizontal to the polymer film substrate.

In one example, the liquid crystal layer of the active liquid crystal film layer may be designed to be converted from any one state selected from a horizontal alignment state, a vertical alignment state, and a twisted alignment state into another state. In one example, the active liquid crystal layer is switchable between a first alignment state and a second alignment state different from the first alignment state.

In one example, the liquid crystal layer may exist in a horizontal alignment state or a twisted alignment state when no voltage is applied, and may exist in a vertical alignment state when a voltage is applied. In the twisted orientation state, the twist angle may be, for example, greater than about 0 degrees and 360 degrees or less. The liquid crystal cell in the horizontally aligned state may be referred to as an ECB (electrically controllable birefringence) mode liquid crystal cell, and the liquid crystal cell in the twisted aligned state may be referred to as a TN (twisted nematic) mode or STN (super twisted nematic) mode liquid crystal cell. The twist angle of the TN-mode liquid crystal cell may be greater than 0 degree to 90 degrees or less, and according to one embodiment of the present application, the twist angle in the TN-mode may be about 10 degrees or more, about 20 degrees or more, about 30 degrees or more, about 40 degrees or more, about 50 degrees or more, about 60 degrees or more, about 70 degrees or more, about 80 degrees or more, or about 90 degrees or more.

In the STN mode, the twist angle may be about 100 degrees or more, about 110 degrees or more, about 120 degrees or more, about 130 degrees or more, about 140 degrees or more, about 150 degrees or more, about 160 degrees or more, about 170 degrees or more, about 180 degrees or more, about 190 degrees or more, about 200 degrees or more, about 210 degrees or more, about 220 degrees or more, about 230 degrees or more, about 240 degrees or more, about 250 degrees or more, about 260 degrees or more, about 270 degrees or more, about 280 degrees or more, about 290 degrees or more, about 300 degrees or more, about 310 degrees or more, about 320 degrees or more, about 330 degrees or more, about 340 degrees or more, or about 350 degrees or more, or may be about 270 degrees, or about 360 degrees or more.

The liquid crystal molecules in the horizontally aligned liquid crystal layer may exist in a state where the optical axis is horizontally aligned with the plane of the liquid crystal layer. For example, the optical axes of the liquid crystal molecules may form an angle in a range of about 0 to 20 degrees, 0 to 15 degrees, 0 to 10 degrees, or 0 to 5 degrees, or about 0 degrees, with respect to the plane of the liquid crystal layer. The optical axes of the liquid crystal molecules in the horizontally aligned liquid crystal layer may be parallel to each other and may form an angle in the range of 0 to 10 degrees, 0 to 5 degrees, or about 0 degrees, for example.

In the twist-aligned liquid crystal layer, the liquid crystal molecules may have a helical structure in which the optical axis is aligned in the layer while being twisted along a virtual helical axis. The optical axis of the liquid crystal molecules may mean a slow axis of the liquid crystal molecules, wherein the slow axis of the liquid crystal molecules may be parallel to a long axis of the rod-shaped liquid crystal molecules. The spiral axis may be formed parallel to a thickness direction of the liquid crystal layer. In this specification, the thickness direction of the liquid crystal layer may mean a direction parallel to a virtual line connecting the lowermost portion and the uppermost portion of the liquid crystal layer at the shortest distance. In one example, the thickness direction of the liquid crystal layer may be a direction parallel to a virtual line formed in a direction perpendicular to the surface of the polymer substrate. In the present specification, the twist angle means an angle formed by an optical axis of liquid crystal molecules existing at the lowermost portion of the twist-aligned liquid crystal layer and an optical axis of liquid crystal molecules existing at the uppermost portion.

The liquid crystal molecules in the vertically aligned liquid crystal layer may exist in a state where the optical axis is aligned perpendicular to the plane of the liquid crystal layer. For example, the optical axes of the liquid crystal molecules may form an angle of about 70 to 90 degrees, 75 to 90 degrees, 80 to 90 degrees, or 85 to 90 degrees, preferably 90 degrees, with respect to the plane of the liquid crystal layer. The optical axes of the plurality of liquid crystal molecules in the vertically aligned liquid crystal layer may be parallel to each other and may form an angle in the range of, for example, 0 to 10 degrees or 0 to 5 degrees or about 0 degrees.

A ratio (d/p) of a thickness (d) to a pitch (p) of the liquid crystal layer in the twist-aligned liquid crystal layer may be 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less. If the ratio (d/p) is outside the range, e.g., greater than 1, a finger domain may occur. The ratio (d/p) may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, or 0.5 or greater. Here, the thickness (d) of the liquid crystal layer may be synonymous with the cell gap of the liquid crystal cell.

The pitch (p) of the twisted-aligned Liquid crystal layer can be measured by a measurement method using a wedge-shaped cell, and specifically, it can be measured by the method described in Simple method for acquisition measurement of the cholesteric pitch using a "stripe-wedge graded-column-Cano cell (Liquid Crystals, volume 35, No. 7, month 7 2008, pages 789 to 791) of D.Podolsky et al.

The liquid crystal layer may further include a chiral dopant for twist alignment. The chiral agent that may be contained in the liquid crystal layer may be used without particular limitation as long as it can induce desired rotation without deteriorating liquid crystallinity such as nematic regularity. A chiral agent for inducing rotation in liquid crystal molecules needs to include at least chirality in the molecular structure. For example, a chiral agent can be exemplified as a compound having one or two or more asymmetric carbons; compounds having asymmetric points on the heteroatom, such as chiral amines or chiral sulfoxides; or compounds having axially asymmetric optically active sites, such as polyenes or binaphthols. The chiral agent may be, for example, a low molecular weight compound having a molecular weight of 1,500 or less. As chiral agent, also commercially available chiral nematic liquid crystals may be used, for example chiral dopant liquid crystal S-811 available from Merck co., ltd or LC756 available from BASF.

The application ratio of the chiral dopant is selected to achieve the above ratio (d/p), and is not particularly limited. Generally, the content (% by weight) of the chiral dopant is calculated by an equation of 100/HTP (helical twisting power) × pitch (nm), and an appropriate ratio may be selected in consideration of a desired pitch with reference to the method.

The thickness of the liquid crystal layer may be appropriately selected in consideration of the object of the present application. The thickness of the liquid crystal layer may be, for example, about 0.01 μm or more, 0.1 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, or 10 μm or more. The upper limit of the thickness of the liquid crystal layer may be, for example, about 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. When the thickness of the liquid crystal layer satisfies the above range, a light modulation device having excellent variable reflectance characteristics can be provided. In one example, the thinner the thickness of the liquid crystal layer is in the above range, the more excellent the variable reflectance characteristic of the light modulation device can be provided.

As the above-described alignment film, the light modulation device may further include a first alignment film and a second alignment film respectively present inside the first polymer film substrate and the second polymer film substrate. In this specification, the inner side of the first polymer film substrate and the second polymer film substrate may mean a side where the light modulation layer is present, and the outer side may mean a side opposite to the side where the light modulation layer is present.

As the first alignment film and the second alignment film, a horizontal alignment film or a vertical alignment film may be applied. In one example, the first alignment film and the second alignment film may all be horizontal alignment films. In another example, either one of the first alignment film and the second alignment film may be a horizontal alignment film, and the other may be a vertical alignment film. According to the light modulation element of the present application, when the horizontal alignment film and the vertical alignment film are applied to the first alignment film and the second alignment film, respectively, the driving voltage characteristics can be improved as compared with the case where the horizontal alignment film is applied to each of the first alignment film and the second alignment film.

The light modulation device can adjust the transmittance, reflectance, and haze by adjusting the alignment state of the liquid crystal layer according to whether or not a voltage is applied. The alignment state of the liquid crystal layer may be controlled by pre-tilt of the alignment film.

In this specification, the pretilt may have an angle and a direction. The pretilt angle may be referred to as the polar angle and the pretilt direction may also be referred to as the azimuthal angle.

The pretilt angle may mean an angle formed by the optical axis of the liquid crystal molecules with respect to the horizontal plane of the alignment film. In one example, the pretilt angle of the vertical alignment film may be about 70 to 90 degrees, 75 to 90 degrees, 80 to 90 degrees, or 85 to 90 degrees. In one example, the pretilt angle of the horizontal alignment film may be about 0 to 20 degrees, 0 to 15 degrees, 0 to 10 degrees, or 0 to 5 degrees.

The pretilt direction may mean a direction in which the optical axes of the liquid crystal molecules are projected on a horizontal plane of the alignment film. The pretilt direction may be an angle formed by the projection direction and a horizontal axis (WA) of the liquid crystal layer. In this specification, the horizontal axis (WA) of the liquid crystal layer may mean a direction parallel to the long axis direction of the liquid crystal layer, or a direction parallel to a line connecting both eyes of an observer wearing eyewear or an observer observing a display device when the light modulation element is applied to the eyewear or the display device such as a TV.

The pretilt directions of the first and second alignment films may be appropriately adjusted in consideration of the orientation of the liquid crystal layer. In one example, the pretilt directions of the first and second alignment films may be parallel to each other for horizontal alignment, the pretilt directions of the first and second alignment films may form 90 degrees to each other for twisted alignment having a twist angle of 90 degrees, and the pretilt directions of the first and second alignment films may be parallel to each other for twisted alignment having a twist angle of 360 degrees. When the pretilt directions of the first and second alignment films are parallel to each other, the pretilt directions of the first and second alignment films may be antiparallel to each other, and for example, may be formed at 170 to 190 degrees, 175 to 185 degrees, preferably 180 degrees, from each other.

The alignment film may be selected and used without particular limitation as long as it has an alignment ability with respect to an adjacent liquid crystal layer. As the alignment film, for example, a contact type alignment film such as a rubbing alignment film, or a photo alignment film capable of exhibiting alignment characteristics by including a photo alignment film compound through a non-contact method such as irradiation of linearly polarized light is known.

It is known to adjust the pretilt direction and angle of a rubbing alignment film or a photo-alignment film. In the case of rubbing the alignment film, the pretilt direction may be parallel to the rubbing direction, and the pretilt angle may be achieved by controlling rubbing conditions (e.g., pressure conditions at the time of rubbing, rubbing strength, etc.). In the case of a photo-alignment film, the pretilt direction may be controlled by the direction of polarized light to be irradiated, or the like, and the pretilt angle may be controlled by the angle of light irradiation, the intensity of light irradiation, or the like.

In one example, each of the first alignment film and the second alignment film may be a rubbing alignment film. When the rubbing directions of the first and second alignment films are disposed parallel to each other, the rubbing directions of the first and second alignment films may be antiparallel to each other, and for example, may be formed 170 to 190 degrees, 175 to 185 degrees, preferably 180 degrees, to each other. The rubbing direction may be determined by measuring the pre-tilt angle, and since the liquid crystal is generally placed along the rubbing direction while generating the pre-tilt angle, the rubbing direction may be measured by measuring the pre-tilt angle. In one example, the lateral directions of the first and second polymer film substrates may each be parallel to the rubbing axis of either one of the first and second alignment films.

The light modulation device may further include a first electrode layer and a second electrode layer as electrode layers, which are present inside the first polymer film substrate and the second polymer film substrate, respectively. When the light modulation device includes the first alignment film and the second alignment film, the first electrode layer may be present between the first polymer film substrate and the first alignment film, and the second electrode layer may be present between the second polymer film substrate and the second alignment film.

The light modulation elements may also include an anti-reflective layer. In one example, the light modulation element may further include a first anti-reflection layer and/or a second anti-reflection layer respectively present outside the first polymer film substrate and/or the second polymer film substrate. As the antireflection layer, a known antireflection layer may be used in consideration of the object of the present application, and for example, an acrylate layer may be used. The thickness of the anti-reflection layer may be, for example, 200nm or less or 100nm or less.

The light modulation element may further include an ultraviolet absorbing layer. In one example, the light modulation element may further include a first ultraviolet absorbing layer and a second ultraviolet absorbing layer respectively present outside the first polymer film substrate and the second polymer film substrate. As the ultraviolet absorbing layer, known ones can be appropriately selected and used in consideration of the object of the present application.

In one example, the light modulation device may be formed by directly coating an anti-reflection layer, an ultraviolet absorption layer, or the like on the polymer film substrate. It may be advantageous in terms of index matching and coating process optimization if a first polymer film substrate and a second polymer film substrate are used. In this case, there is an advantage that the process can be simplified and the thickness of the element can be reduced. In another example, in a light modulation device, an anti-reflective layer or an ultraviolet absorbing layer may be formed on one side of a base film, and the base film may be attached to a polymer film substrate via a pressure sensitive adhesive or an adhesive.

The light modulation device of the present application may further include a reflective layer and a light modulation film layer (active liquid crystal film layer).

In a first embodiment, the reflective layer may be a specular reflective layer. In this case, the light modulation device may further include a quarter wave plate between the active liquid crystal film layer and the reflective layer.

The quarter wave plate may be coated directly on one side of the polymer film substrate of the active liquid crystal film layer, or may be attached via a pressure sensitive adhesive or adhesive. The quarter-wave plate may mean a retardation layer having a quarter-wavelength phase retardation characteristic. In the present specification, the term "n-wavelength phase retardation characteristic" may mean a characteristic that incident light can be phase-delayed by n times the wavelength of the incident light in at least a part of the wavelength range. The in-plane retardation of the quarter-wave plate for a wavelength of 550nm may be, for example, in the range of 110nm to 220nm or 130nm to 170 nm.

The quarter wave plate may be a liquid crystal film or a polymer stretched film.

The liquid crystal film may include a polymerizable liquid crystal compound in a polymerized state. In the present application, the "polymerizable liquid crystal compound" may mean a compound including a moiety capable of exhibiting liquid crystallinity (e.g., a mesogen skeleton) and including one or more polymerizable functional groups. The phrase "including a polymerizable liquid crystal compound in a polymerized form" may mean a state in which the liquid crystal compound is polymerized to form a skeleton, such as a main chain or a side chain, of a liquid crystal polymer in a liquid crystal polymer film. The polymerizable liquid crystal compound may be contained in the liquid crystal film, for example, in a horizontally aligned state.

The polymer stretched film may be, for example, a film in which a light-transmitting polymer film capable of imparting optical anisotropy by stretching is stretched in a suitable manner. The polymer film may be exemplified by, for example, a polyolefin film such as a polyethylene film or a polypropylene film, a cycloolefin polymer (COP) film such as a polynorbornene film, a polyvinyl chloride film, a polyacrylonitrile film, a polysulfone film, a polyacrylate film, a polyvinyl alcohol film, or a cellulose ester-based polymer film such as a TAC (triacetyl cellulose) film, or a copolymer film of two or more monomers among monomers forming the polymer, or the like. In one example, as the polymer film, a cycloolefin polymer film may be used. Here, the cyclic olefin polymer may be exemplified by a ring-opened polymer of cyclic olefin such as norbornene or a hydrogenated product thereof, an addition polymer of cyclic olefin, a copolymer of other comonomer such as α -olefin and cyclic olefin, or a graft polymer in which a polymer or copolymer is modified with unsaturated carboxylic acid or a derivative thereof, and the like, but is not limited thereto.

In one example, the slow axis of the quarter-wave plate and the average optical axis of the liquid crystal molecules of the active liquid crystal layer may be in a range of 40 degrees to 50 degrees or 43 degrees to 47 degrees, or about 45 degrees, with each other when no voltage is applied. In the present specification, the average optical axis may mean a vector sum of optical axes of liquid crystal molecules of the liquid crystal layer.

When the angle formed by the slow axis of the quarter-wave plate and the average optical axis of the liquid crystal molecules of the liquid crystal layer is within the above range, excellent anti-reflection characteristics may be exhibited in the blocking state, and thus it may be advantageous to improve variable reflectance characteristics.

In the light modulation device, the reflective layer may be present on one side of the quarter-wave plate. Further, the reflective layer may be coated directly on one side of the quarter wave plate, or may be attached via a pressure sensitive adhesive or adhesive.

The reflective layer may have a specular reflection characteristic. The specular reflection characteristic may be referred to as regular reflection or specular reflection. In one example, the reflective layer may have a reflectance of 20% to 100% for light having a wavelength of 400nm to 700 nm.

The reflective layer may be, for example, a metal thin film layer containing a metal having a high reflectance to all visible light, such as silver, gold, magnesium, nickel, bismuth, chromium, copper, calcium, strontium, aluminum, or an alloy thereof.

The light modulation device of the first embodiment can exhibit variable reflectance characteristics according to the alignment state of the liquid crystal layer depending on whether or not a voltage is applied. That is, the light modulation device of the first embodiment can be switched between the low reflection mode state and the high reflection mode state as described above.

The light modulation device may be in a blocking state indicating a minimum reflectance when no voltage is applied to the liquid crystal layer, and may be in a reflective state indicating a maximum reflectance when a voltage is applied.

In one example, the difference between the reflectance of the light modulation device when a voltage of 15V is applied and the reflectance when no voltage is applied may be 20% to 60%.

In a second embodiment of the present application, the reflective layer may be a reflective polarizer. In this case, as the reflective layer, two reflective polarizers may be included. The light modulating means may comprise a first reflective polarizer and a second reflective polarizer as reflective layers. For example, the second embodiment may include, in order, the active liquid crystal film layer and the first reflective polarizer described above, an additional light modulating film layer, and a second reflective polarizer.

The light modulation film layer may be configured similarly to the active liquid crystal film layer, and may include, for example, a third polymer film substrate and a fourth polymer film substrate disposed opposite to each other, and an active liquid crystal layer existing between the third polymer film substrate and the fourth polymer film substrate and containing a liquid crystal compound. The third and fourth substrates may be the same kind of asymmetric film substrate as the above-described active liquid crystal film layer substrate, or may be other kinds of substrates.

The active liquid crystal layer (hereinafter, may be referred to as a second liquid crystal layer) of the light modulation film layer may not contain the dichroic dye. The contents described in the item of liquid crystal molecules of the active liquid crystal film layer may be equally applied to the liquid crystal compound of the second liquid crystal layer. Hereinafter, the liquid crystal layer including the liquid crystal molecules (liquid crystal host) and the dichroic dye of the above-described active liquid crystal film layer may be referred to as a first liquid crystal layer for convenience.

The first liquid crystal layer and the second liquid crystal layer may change their alignment states depending on whether or not a voltage is applied. The voltage may be applied in a direction perpendicular to the polymer film substrate.

In a second embodiment, the first liquid crystal layer may be designed to switch between a vertically aligned state and a horizontally aligned state. For example, it may exist in a vertically aligned state when no voltage is applied, and may exist in a horizontally aligned state when a voltage is applied. Such a liquid crystal layer may be referred to as a VA (vertical alignment) mode liquid crystal layer.

The second liquid crystal layer may be switched between a horizontal alignment state and a twisted alignment state. For example, it may exist in a twisted alignment state when no voltage is applied, and may exist in a horizontal alignment state when a voltage is applied. Such a liquid crystal cell may be referred to as a TN (twisted nematic) mode liquid crystal cell. The twist angle in the twisted orientation state may be greater than 0 degrees to 90 degrees or less, and according to one embodiment of the present application, the twist angle in the TN mode may be about 10 degrees or more, about 20 degrees or more, about 30 degrees or more, about 40 degrees or more, about 50 degrees or more, about 60 degrees or more, about 70 degrees or more, about 80 degrees or more, or about 90 degrees.

The above can be equally applied to the states of the optical axes of the liquid crystal molecules in the vertically aligned liquid crystal layer and the optical axes of the liquid crystal molecules in the horizontally aligned liquid crystal layer.

Further, the above can be equally applied to the problems regarding the state of the optical axis of the liquid crystal molecules in the twist-aligned liquid crystal layer, the twist angle, the ratio (d/p) between the thickness (d) and the pitch (p), and the measurement method thereof.

The liquid crystal layer may further contain a chiral dopant for twisted alignment, wherein the problems regarding the specific type and ratio of the chiral dopant used are also the same as described above.

The thickness of the first liquid crystal layer and/or the second liquid crystal layer may be appropriately selected in consideration of the purpose of the present application. The thickness of the liquid crystal layer may be, for example, about 0.01 μm or more, 0.1 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, or 10 μm or more. The upper limit of the thickness of the liquid crystal layer may be, for example, about 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. When the thickness of the liquid crystal layer satisfies the above range, a light modulation device having excellent variable reflectance characteristics can be provided. In one example, the thinner the thickness of the liquid crystal layer is within the above range, the more excellent the variable reflectance characteristic of the light modulation device can be provided.

The light modulation device may include an alignment film present on the polymer film substrate of the active liquid crystal film layer and an alignment film present on the substrate of the light modulation film layer. Hereinafter, for convenience of explanation, the four alignment films are referred to as first to fourth alignment films, respectively, wherein the first alignment film and the second alignment film are alignment films inside the substrate of the active liquid crystal film layer, respectively, and the third alignment film and the fourth alignment film are alignment films inside the substrate of the light modulation film layer, respectively. In this specification, the inner side of the substrate is a surface of the substrate facing the light modulation layer or the active liquid crystal layer.

A horizontal alignment film or a vertical alignment film may be applied to each of the first to fourth alignment films. In one example, each of the first alignment film and the second alignment film may be a vertical alignment film. In one example, each of the third and fourth alignment films may be a horizontal alignment film, or either one of the third and fourth alignment films may be a horizontal alignment film and the other may be a vertical alignment film. According to the light modulation device of the present application, the case where the horizontal alignment film and the vertical alignment film are applied to the third alignment film and the fourth alignment film, respectively, can improve the driving voltage characteristics, as compared to the case where the horizontal alignment film is applied to the third alignment film and the fourth alignment film, respectively.

The light modulation device may adjust transmittance, reflectance, and haze by adjusting an alignment state of the liquid crystal layer according to whether or not a voltage is applied. The alignment state of the liquid crystal layer may be controlled by the pre-tilt of the alignment film, wherein the content of the pre-tilt is similar to that described above.

The pretilt directions of the first and second alignment films may be appropriately adjusted in consideration of the orientation of the first liquid crystal layer. Further, the pretilt directions of the third and fourth alignment films may be appropriately adjusted in consideration of the orientation of the second liquid crystal layer. In one example, the pretilt directions of the first and second alignment films may be parallel to each other for vertical alignment when no voltage is applied, and the pretilt directions of the first and second alignment films may form 90 degrees with each other for twisted alignment having a twist angle of 90 degrees. When the pretilt directions of the first and second alignment films are parallel to each other, the pretilt directions of the first and second alignment films may be antiparallel to each other, for example, they may be in the range of 170 degrees to 190 degrees or 175 degrees to 185 degrees, or about 180 degrees, with each other. In one example, the lateral directions of the first and second polymer film substrates may each be parallel to the rubbing axis of either one of the first and second alignment films. In one example, the lateral directions of the third and fourth polymer film substrates may each be parallel to the rubbing axis of any one of the third and fourth alignment films.

The alignment film may be selected and used without particular limitation as long as it has an alignment ability with respect to an adjacent liquid crystal layer, and the specific type is also similar to the above.

In one example, each of the first to fourth alignment films may be a rubbing alignment film. When the rubbing directions of the first and second alignment films are disposed parallel to each other, the rubbing directions of the first and second alignment films may be antiparallel to each other, for example, they may be in the range of 170 degrees to 190 degrees or 175 degrees to 185 degrees, or about 180 degrees, to each other. The rubbing direction may be determined by measuring the pre-tilt angle, and since the liquid crystal is generally placed along the rubbing direction while generating the pre-tilt angle, the rubbing direction may be measured by measuring the pre-tilt angle.

The light modulation device may further include first and second electrode layers respectively present inside the first and second polymer film substrates, and may further include third and fourth electrode layers respectively present inside the third and fourth polymer film substrates. When the light modulation device includes the first, second, third, and fourth alignment films, the first electrode layer may be present between the first polymer film substrate and the first alignment film, the second electrode layer may be present between the second polymer film substrate and the second alignment film, the third electrode layer may be present between the third polymer film substrate and the third alignment film, and the fourth electrode layer may be present between the fourth polymer film substrate and the second alignment film.

The light modulation element of the second embodiment may further include an antireflection layer, an ultraviolet absorbing layer, and the like, similarly to the first embodiment.

The light modulating device may include a first reflective polarizer of an active liquid crystal film layer including a first liquid crystal layer. The first reflective polarizer may be coated directly on one side of the polymer film substrate of the active liquid crystal film layer, or may be attached via a pressure sensitive adhesive or adhesive.

The reflective polarizer may have selective transmission and reflection properties. For example, the reflective polarizer may have the property of transmitting one of the transverse wave component and the longitudinal wave component of light and reflecting the other component. When light is incident on the reflective polarizer, the light transmitted through the reflective polarizer and the light reflected from the reflective polarizer may have polarization characteristics. In one example, the polarization direction of the transmitted light and the polarization direction of the reflected light may be orthogonal to each other. That is, the reflective polarizer may have a reflection axis and a transmission axis orthogonal to the planar direction.

As the reflective polarizer, for example, a reflective polarizer called a so-called DBEF (dual brightness enhancement film) or a reflective polarizer formed by coating a liquid crystal compound such as LLC (lyotropic liquid crystal) can be used.

Since the reflective polarizer has a characteristic of transmitting most of one of the transverse wave component and the longitudinal wave component of light and reflecting most of the other component, it can be implemented in the form of a half mirror (half mirror). In one example, the reflective polarizer may have a reflectivity of about 50% or greater for unpolarized incident light. According to an example of the present application, DBEF (dual brightness enhancement film) can be used, for example, as a reflective polarizer.

In one example, the reflection axis of the first reflective polarizer and the average optical axis of the liquid crystal molecules of the liquid crystal layer may form 0 to 10 degrees, 0 to 5 degrees, or about 0 degrees when the first liquid crystal layer is horizontally oriented. The average optical axis may mean a vector sum of optical axes of liquid crystal molecules in the liquid crystal layer.

When the angle formed by the reflection axis of the first reflective polarizer and the average optical axis of the liquid crystal molecules in the first liquid crystal layer is within the above range, excellent antireflection characteristics may be exhibited in the blocking state, and thus it may be advantageous to improve variable reflectance characteristics.

The light modulating means may comprise a light modulating film layer on one side of the first reflective polarizer. The first reflective polarizer may be coated directly on one side of the substrate of the light modulating film layer, or may be attached via a pressure sensitive adhesive or adhesive.

In one example, when the second liquid crystal layer of the light modulating film layer is twist oriented, the reflection axis of the first reflective polarizer and the optical axis of the liquid crystal molecules in the liquid crystal layer that are closest to the first reflective polarizer may form an angle in the range of 80 degrees to 110 degrees or 85 degrees to 105 degrees, or about 90 degrees.

Further, in one example, when the second liquid crystal layer of the light modulating film layer is twist oriented, the reflection axis of the first reflective polarizer and the optical axis of the liquid crystal molecules in the liquid crystal layer that are furthest from the first reflective polarizer may form an angle in the range of 0 degrees to 10 degrees, or 0 degrees to 5 degrees, or an angle of about 0 degrees.

When the angle formed by the reflection axis of the first reflective polarizer and the optical axis of the liquid crystal molecules of the second liquid crystal layer is within the above range, excellent antireflection characteristics may be exhibited in the blocking state, and thus it may be advantageous to improve variable reflectance characteristics.

The light modulating device may further include a second reflective polarizer on a side of the light modulating film layer having the second liquid crystal layer. The second reflective polarizer may be coated directly on the substrate of the light modulating film layer with the second liquid crystal layer, or may be attached via a pressure sensitive adhesive or adhesives. Unless otherwise stated with respect to the second reflective polarizer, the description with respect to the first reflective polarizer may apply equally.

The reflective axis of the second reflective polarizer may form an angle with the reflective axis of the first reflective polarizer in the range of 0 degrees to 10 degrees or 0 degrees to 5 degrees or about 0 degrees. When the angle formed by the reflection axis of the second reflective polarizer and the reflection axis of the first reflective polarizer is within the above range, excellent antireflection characteristics may be exhibited in the blocking state, and thus it may be advantageous to improve variable reflectance characteristics.

The light modulation device may exhibit a reflectance variable characteristic according to an alignment state of the liquid crystal layer according to whether or not a voltage is applied. That is, the light modulation device can be switched between the high reflection mode and the low reflection mode as described above.

The light modulation device may take a reflective state that exhibits the maximum reflectance when no voltage is applied to the liquid crystal layer and may take a blocking state that exhibits the minimum reflectance when a voltage is applied. The light modulation device has excellent variable reflectance characteristics depending on whether or not a voltage is applied. In one example, the difference between the reflectance of the light modulation device when a voltage of 10V is applied and the reflectance when no voltage is applied may be 30% to 50%. The reflectivity may be a value measured at an inclination angle of 20 degrees.

The light modulation device can be applied to various applications requiring variable reflectance characteristics. Applications requiring variable reflectance properties may be exemplified as openings in enclosed spaces including buildings, containers, or vehicles (e.g., variable materials for vehicles, variable mirrors, interior mirrors, windows or sunroofs), eyewear, or the like. Here, in the scope of eyewear, all eyewear formed so that an observer can observe the outside through lenses, such as general glasses, sunglasses, sports goggles or helmets, or instruments for experiencing augmented reality, may be included.

A typical application where light modulating devices may be applied is eyewear. When the light modulation device is applied to the eyewear, the structure of the eyewear is not particularly limited. That is, the light modulation element may be mounted and applied to a left eye lens and/or a right eye lens having a known eyewear structure.

For example, eyewear may include a left eye lens and a right eye lens; and a frame for supporting the left and right eye glasses.

Fig. 2 is an exemplary schematic diagram of eyewear, which is a schematic diagram of eyewear including a frame 12 and left and right eye lenses 14, but the structure of eyewear to which the light modulation device can be applied is not limited to fig. 2. In the eyewear, the left and right eye lenses may each comprise a light modulation device. Such a lens may include only the light modulation device, or may also include other configurations.

Advantageous effects

The present application can provide a light modulation device excellent in both mechanical and optical characteristics by applying an optically and mechanically anisotropic polymer film as a substrate.

Drawings

Fig. 1 is a schematic diagram of an exemplary light modulation device of the present application.

Figure 2 schematically shows eyewear.

Fig. 3 and 4 show the durability evaluation results of the examples and comparative examples.

Detailed Description

Hereinafter, the present application will be specifically described by way of examples, but the scope of the present application is not limited by the following examples.

The polymer film substrates used in the examples or comparative examples were PC (polycarbonate) film substrates (PC substrate, thickness: 100 μm, manufacturer: Teijin, product name: PFC100-D150), which are isotropic film substrates generally used as substrates; and a PET (polyethylene terephthalate) film substrate (SRF substrate, thickness: 80 μm, manufacturer: Toyobo, product name: TA044), which is an asymmetric substrate according to the present application, and the following physical properties were measured in a state where an ITO (indium tin oxide) film having a thickness of about 20nm was formed on one side of each film substrate.

1. Phase retardation assessment of polymer film substrates

The in-plane retardation value (Rin) of the polymer film substrate for light having a wavelength of 550nm was measured using a UV/VIS spectroscope 8453 instrument from Agilent co. Two polarizers were installed in a UV/VIS spectroscope such that transmission axes of the polarizers were orthogonal to each other, and a polymer film was installed between the two polarizers such that slow axes of the polymer film and the transmission axes of the two polarizers, respectively, formed at 45 degrees, and then transmittance according to wavelength was measured. The phase retardation magnitude of each peak is obtained from the transmittance map according to the wavelength. Specifically, the waveform in the transmittance map according to the wavelength satisfies the following equation a, and the maximum peak (Tmax) condition in the sinusoidal waveform satisfies the following equation B. In the case of λ max in equation a, since T of equation a is the same as T of equation B, the equation is extended. Since the equations are also extended for n +1, n +2, and n +3, the n and n +1 equations are arranged to eliminate R, and n is arranged into the λ n and λ n +1 equations, the following equation C is derived. Since n and λ can be known based on the fact that T of equation a is the same as T of equation B, R is obtained for each of λ n, λ n +1, λ n +2, and λ n + 3. A linear trend line of R values according to the wavelength of 4 points was obtained, and the R value for equation 550nm was calculated. The function of the linear trend line is Y ═ ax + b, where a and b are constants. The value of Y when x of the function is replaced with 550nm is the value of Rin for light having a wavelength of 550 nm.

[ equation A ]

T＝sin²[(2πR/λ)]

[ equation B ]

T＝sin²[((2n+1)π/2)]

[ equation C ]

n＝(λn-3λn+1)/(2λn+1+1-2λn)

In the above, R denotes an in-plane retardation (Rin), λ denotes a wavelength, and n denotes a nodal degree (nodal degree) of a sinusoidal waveform.

2. Evaluation of tensile Properties and thermal expansion coefficients of Polymer film substrates

Tensile strength tests were performed according to the standard by applying force at a tensile speed of 10 mm/min at room temperature (25 ℃) using a UTM (universal testing machine) apparatus (Instron3342) to measure the elastic modulus (young's modulus), elongation and maximum stress of the polymer film substrate. In this case, each sample was prepared by cutting the polymer film substrate to have a width of about 10mm and a length of about 30mm, and both ends in the longitudinal direction were each wound with a tape for 10mm and fixed to the apparatus, and then evaluated.

A length expansion test was performed according to a standard while increasing the temperature from 40 ℃ to 80 ℃ at a rate of 10 ℃/min using a TMA (thermo-mechanical analysis) apparatus (meteler Toledo, SDTA840) to measure the thermal expansion coefficient. In the measurement, the length of the sample in the measurement direction was set to 10mm, and the load was set to 0.02N.

The evaluation results of the physical properties of each film substrate measured in the above-described manner are shown in table 1 below.

In table 1 below, MD and TD are MD direction (machine direction) and TD direction (transverse direction) of the PC substrate and SRF substrate as the stretched films, respectively, and 45 is a direction forming 45 degrees with both MD direction and TD direction.

[ Table 1]

Example 1.

Two SRF substrates were used to fabricate a light modulation device. An alignment film was formed on an ITO (indium tin oxide) film (electrode layer) of an SRF substrate (width: 15cm, length: 5cm) to prepare a first substrate. As the alignment film, an alignment film obtained by rubbing a polyimide-based horizontal alignment film (SE-7492, Nissan) having a thickness of 300nm with a rubbing cloth was used. The second substrate is prepared in the same manner as the first substrate. The first and second substrates were disposed opposite to each other such that their alignment films faced each other, a GHLC mixture (MDA-16-1235, Merck) including a liquid crystal compound having positive dielectric constant anisotropy and refractive index anisotropy (Δ n) of 0.13 and a dichroic dye was disposed therebetween, and then the frame was sealed to prepare an active liquid crystal film layer. The active liquid crystal film layer is in ECB mode and the cell gap is 6 μm. Here, the TD directions (slow axis directions) of the first and second substrates are each 0 degree based on the rubbing axis of the first substrate alignment film, and the rubbing directions of the first and second alignment films are antiparallel to each other. Subsequently, a normal mirror (reflective layer) is disposed on one side of the active liquid crystal film layer to manufacture an optical device. The reflective layer is a normal mirror with an average reflectance of about 95% for light of 400nm to 700 nm.

Comparative example 1.

A light modulation device was manufactured in the same manner as in example 1 except that a PC substrate was used as the substrate.

Test example 1.

An eyewear element of the type shown in fig. 3 and 4 was manufactured using the light modulation devices of example 1 and comparative example 1, and a thermal shock test was performed in a state where the element was bent. The thermal shock test was performed by setting the following steps: the temperature of the eyewear was raised from about-40 ℃ to 90 ℃ at a temperature ramp-up rate of about 16.25 ℃/minute, then held for 10 minutes, and again lowered from 90 ℃ to-40 ℃ at a temperature ramp-down rate of about 16.25 ℃/minute, then held for 10 minutes, which was a cycle and the cycle was repeated 500 times, with the test being performed with the eyewear attached to a curved clamp having a radius of curvature of about 100R. Fig. 3 shows the case of example 1, and fig. 4 shows the case of comparative example 1, in which in the case of comparative example 1, severe cracks were observed as in the drawing.

Comparative example 2.

A light modulation device was manufactured in the same manner as in embodiment 1 except that the first directions (TD directions) of the first substrate and the second substrate were set at 90 degrees to each other. At this time, the first direction of the first substrate is 0 degree and the first direction of the second substrate is 90 degrees based on the rubbing direction of the alignment film on the first substrate.

Comparative example 3.

A light modulation device was manufactured in the same manner as in embodiment 1 except that the first directions (TD directions) of the first substrate and the second substrate were set at 90 degrees to each other. At this time, the first direction of the first substrate is 45 degrees and the first direction of the second substrate is 135 degrees based on the rubbing direction of the alignment film on the first substrate.

Test example 2.

The generation of voids was evaluated while the devices of example 1, comparative examples 2 and 3 were each stored at 60 ℃ and 85% relative humidity, and the results are shown in table 2 below. Specifically, it was evaluated whether or not a visually observed void occurred therein while the light modulation layer was kept under the above-described conditions. Typically, the visually observed size of the voids is about 10 μm.

[ Table 2]

As a result of table 2, in the case of comparative examples 2 and 3, voids were observed in all the initially introduced samples within 500 hours, showing a void occurrence rate of 100%, and the time for which voids were first observed was also within 120 hours and 144 hours, respectively.

On the other hand, in the case of example 1, no voids were observed within 500 hours, and the time for which voids were first observed was also about 504 hours.

Examples 2 to 4.

A quarter-wave plate was placed between the active liquid crystal film layer and the reflective layer of the optical device of example 1 to prepare a light modulation device (example 2). The quarter-wave plate is a retardation film formed of TAC (triacetyl cellulose) film.

The optical modulation device was evaluated for electro-optical characteristics and occurrence of an iridescence phenomenon. The electro-optical characteristics of the light modulation device are evaluated by measuring the change in reflectance depending on whether or not a voltage is applied. Specifically, while an AC power source was connected to the electrode layer of the active liquid crystal film layer and driven, the reflectance according to the applied voltage was measured using a reflective spectroscope (CM-2600d, Konica Minolta). The reflectance is an average value of reflectance for light having a wavelength of 380nm to 780 nm.

The evaluation of the rainbow phenomenon is a cognitive evaluation, which evaluates that the rainbow phenomenon occurs when two or more patterns exhibiting different brightness, rather than the same brightness, are generated in the sample.

In the following evaluation examples, TN _90 ° is the result of the case where the active liquid crystal layer is composed of the TN mode having a twist angle of 90 degrees (embodiment 3), and STN _360 ° is the case where the active liquid crystal layer is composed of the STN mode having a twist angle of 360 degrees (embodiment 4).

In the case of example 2, an active liquid crystal film layer was prepared in the same manner as in the case of example 1 where the active liquid crystal film layer was formed, except that 0.118 wt% of a chiral dopant (S811, Merck) was added to the GHLC composition and used, and the film layers were synthesized such that rubbing directions of alignment films of the first and second substrates were 90 degrees to each other. Further, in the case of example 3, an active liquid crystal film layer was prepared in the same manner as in the case of example 1 where the active liquid crystal film layer was formed, except that 0.656 wt% of a chiral dopant (S811, Merck) was added to the GHLC composition, wherein the ratio (d/p) of the thickness (cell gap: d) to the pitch (p) of the liquid crystal layer in STN mode was about 0.95.

In the following evaluation examples, "0V _ R" is the reflectance when no voltage is applied, "15V _ R" is the reflectance when a voltage of 15V is applied, and "Δ T" is the value of "15V _ R" - "0V _ R".

[ Table 3]

Example 5

Two active liquid crystal film layers were prepared using SRF substrates. The SRF substrate was cut to have a width of 15cm and a length of 5cm, respectively, and an alignment film was formed on one side of an ITO (indium tin oxide) film (electrode layer) to prepare two substrates. As the alignment film, an alignment film obtained by rubbing a polyimide-based vertical alignment film (5661LB3, Nissan) having a thickness of 300nm with a rubbing cloth was used. The prepared two substrates were disposed opposite to each other such that their alignment films faced each other, a GHLC composition including a liquid crystal having a negative dielectric constant anisotropy (k) and a refractive index anisotropy (Δ n) of 0.13 and a dichroic dye (MAT-16-568, Merck) was disposed therebetween, and the frame was sealed with a sealant to form a first active liquid crystal film layer. At this time, the transverse directions (TD directions) of the first and second substrates are each 0 degree based on the rubbing axis of the first polymer film substrate, and the rubbing directions of the alignment films of the first and second substrates are antiparallel to each other. The first active liquid crystal film layer was a VA mode liquid crystal cell, and the cell gap was 6 μm.

A second active liquid crystal film layer was prepared in the same manner as the first active liquid crystal film layer except that a horizontal alignment film (SE-7492, Nissan) based on polyimide was used as alignment films on both substrates, and the film layers were synthesized such that rubbing directions each formed 90 degrees to each other, but at this time, a liquid crystal layer was formed using a liquid crystal composition in which 0.118 wt% of a chiral dopant (S811, Merck) was added to a liquid crystal (MDA-16-1235, Merck) having positive dielectric constant anisotropy and refractive index anisotropy (Δ n) of 0.13. The second active liquid crystal film layer was a TN-mode liquid crystal cell having a twist angle of 90 degrees, and the cell gap was 6 μm.

DBEF (dual brightness enhancement film, 3M) having a reflectance of 45% for unpolarized incident light having a wavelength of 380nm to 780nm was prepared as the first reflective polarizer and the second reflective polarizer.

A first active liquid crystal film layer, a first reflective polarizer, a second active liquid crystal film layer, and a second reflective polarizer were laminated in this order to manufacture a light modulation device. The reflection axis of the first reflective polarizer is parallel to the rubbing axis of the alignment film close to the first reflective polarizer of the two alignment films of the first active liquid crystal film layer, and is orthogonal to the rubbing axis of the alignment film close to the first reflective polarizer of the two alignment films of the second active liquid crystal film layer, and the reflection axes of the first reflective polarizer and the second reflective polarizer are parallel to each other.

The optical modulation device was evaluated for electro-optical characteristics and occurrence of an iridescence phenomenon. The electro-optical characteristics of the light modulation device are evaluated by measuring the change in reflectance depending on whether or not a voltage is applied. Specifically, while an AC power source is connected to the first ITO layer and the second ITO layer and driven, the reflectance according to the applied voltage is measured using a reflective spectroscope (CM-2600d, Konica Minolta) in a state where a mirror having a reflectance of 95% or more is arranged on one side of the light modulation device. The reflectance is an average value of reflectance for light having a wavelength of 380nm to 780 nm.

The evaluation of the rainbow phenomenon is a cognitive evaluation, which evaluates that the rainbow phenomenon occurs when two or more patterns exhibiting different brightness, rather than the same brightness, are generated in the sample.

In the following evaluation examples, "0V _ R" is the reflectance when no voltage is applied, "15V _ R" is the reflectance when a voltage of 15V is applied, and "Δ T" is the value of "15V _ R" - "0V _ R". In the following evaluation examples, the reflectance is a result measured for light incident in a direction forming 10 degrees or 20 degrees with the surface normal direction of the light modulation device.

[ Table 4]

Claims (16)

1. A light modulation device includes an active liquid crystal film layer having a first polymer film substrate and a second polymer film substrate disposed opposite to each other, and an active liquid crystal layer existing between the first polymer film substrate and the second polymer film substrate and including a liquid crystal host and a dichroic dye guest,

wherein the active liquid crystal layer is switchable between a first alignment state and a second alignment state different from the first alignment state,

each of the first and second polymeric film substrates having an in-plane retardation of 4,000nm or greater for light having a wavelength of 550nm,

the first polymeric film substrate and the second polymeric film substrate are each stretched polymeric films,

the first direction of each of the first and second polymeric film substrates is a cross direction and the second direction of each of the first and second polymeric film substrates is a machine direction,

a ratio E1/E2 of an elongation E1 in the first direction to an elongation E2 in the second direction perpendicular to the first direction of each of the first and second polymeric film substrates is 3 or more, and

the first and second polymer film substrates are disposed such that an angle formed by the first direction of the first polymer film substrate and the first direction of the second polymer film substrate is in a range of 0 degrees to 10 degrees.

2. The light modulation device according to claim 1, wherein the first polymer film substrate and the second polymer film substrate are each an electrode film substrate in which an electrode layer is formed on one side, and the first polymer film substrate and the second polymer film substrate are disposed such that the electrode layers face each other.

3. The light modulating device of claim 1, wherein the first and second polymer film substrates are polyester film substrates.

4. The light modulating device of claim 1, wherein the first and second polymeric film substrates each have an elongation in the first direction of 15% or greater.

5. The light modulation device of claim 1, wherein the first and second polymer film substrates each have an elongation E3 in a third direction that is greater than an elongation E1 in the first direction, and a ratio E3/E2 of an elongation E3 in the third direction to an elongation E2 in the second direction is 5 or greater, the third direction forming an angle in a range of 40 to 50 degrees with both the first and second directions.

6. The light modulating device of claim 1, wherein a ratio of a coefficient of thermal expansion in the second direction CTE2 to a coefficient of thermal expansion in the first direction CTE1, CTE2/CTE1, of each of the first and second polymeric film substrates is 1.5 or greater.

7. The light modulating device of claim 6, wherein the coefficient of thermal expansion in the second direction CTE2 is in a range of 5ppm/° c to 150ppm/° c.

8. The light modulation device according to claim 1, wherein a ratio YM1/YM2 of an elastic modulus YM1 in the first direction to an elastic modulus YM2 in the second direction of each of the first polymer film substrate and the second polymer film substrate is 1.5 or more.

9. The light modulation device according to claim 8, wherein a modulus of elasticity YM1 in the first direction is in a range of 4GPa to 10 GPa.

10. The light modulating device of claim 1, wherein a ratio of a maximum stress MS1 in the first direction to a maximum stress MS2 in the second direction, MS1/MS2, of each of the first and second polymeric film substrates is 2 or greater.

11. The light modulation device of claim 10, wherein a maximum stress MS1 in the first direction is in a range of 150MPa to 250 MPa.

12. The light modulating device of claim 1, wherein the reflective layer is a specular reflective layer.

13. The light modulation device of claim 12, further comprising a quarter-wave plate between the active liquid crystal film layer and the reflective layer.

14. The light modulation device of claim 1, further comprising a first reflective polarizer and a second reflective polarizer as the reflective layer.

15. The light modulating device of claim 14 further comprising a light modulating film layer having an active liquid crystal layer comprising a liquid crystal compound, wherein the active liquid crystal film layer, the first reflective polarizer, the light modulating film layer, and the second reflective polarizer are included in that order.

16. An eyewear comprising a left eye lens and a right eye lens; and a frame for supporting the left and right eye glasses,

wherein the left eye lens and the right eye lens each comprise the light modulation device of claim 1.

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